Yogurt is a nutritious dairy product which recently has become quite popular. At retail, yogurt is now available in a wide assortment of varieties of texture, fat content and flavor among other attributes. Other than aseptically packaged yogurt, yogurt is traditionally distributed and consumed with a live culture which requires refrigerated distribution.
From a yogurt manufacturing process standpoint, all fruit containing yogurts fall into one of two styles; namely, 1) set yogurts, and 2) stirred style. Within these broad two classifications, numerous yogurt varieties exist.
In the set style, the "yogurt" is charged to its container and allowed to set or increase in viscosity and/or ferment. Usually, an inoculated milk base is charged to the container and allowed to ferment in situ at warm temperatures of about 40.degree. to 50.degree. C. After the desired maturing time, the product is cooled which arrests the culturing activity and also allows the body to set to form the gel-type texture. Set style yogurts have a relatively low initial viscosity (i.e., upon filling of its food package container) and a higher temperature ("temperature of filling") compared to the viscosities of stirred style yogurt products. As the product cools and ferments, its viscosity increases to its final viscosity value. A set style yogurt is characterized by a more firm, gel-like consistency and a higher final viscosity than most stirred style yogurts. In addition to the natural thickening effect of the yogurt culture, a wide variety of thickeners and stabilizers are taught as useful to supplement the yogurt's gel characteristics.
Of course, within this set style, there is a continuum of body firmness. Most set custard style products have quite firm gels although some others are much softer. One variety of a set style yogurt is a "custard" style yogurt. The softer gel products may even be perceived by the consumer as being thinner than even certain stirred style products.
One popular style variant of custard style yogurt is fruit-on-the-bottom, also colloquially referred to as "sundae" style, in which a discrete layer of fruit preserves is on the bottom of the yogurt container and the custard yogurt fills the rest of the container. The fruit preserves have a higher density than the yogurt. Since the yogurt in set style products is still liquid upon charging to the container, the relatively more dense fruit preserves are thus then generally charged first to the container at its bottom and the lighter liquid unset yogurt added thereupon. The yogurt is then allowed to ferment, cool, and set on the top of the fruit preserve. Fruit on the top style products are similarly prepared, except that the containers are typically inverted after having been allowed to set. Typically, the yogurt phase is unflavored, although occasionally sweetened, and of a white or natural color. This white color is in contrast to the separate fruit preserve layer which often contains additional coloring supplemental to that coloring provided by the ingredients of the fruit preserves. Other than for moisture equilibration, the yogurt layer and the fruit preserve layer usually do not intermix over time due to specific growth difference and the binding effect of pectin in the fruit preserves.
Still another variation of the custard style yogurt is what has sometimes colloquially been referred to as "western" or "California" style yogurt which generally is a custard style yogurt with a discrete layer of fruit preserves on the bottom, but wherein the custard yogurt additionally contains a water soluble, natural colorant corresponding to the color of the fruit preserves. Thus, in a product having a strawberry fruit preserve bottom layer, the custard yogurt layer or phase may additionally comprise modest levels of red colorant sufficient to give the yogurt phase a pink color complimentary of the red fruit preserve layer. Frequently, both phases have added water soluble colorants.
In the second general category of yogurt products, the yogurt is of a stirred type. In stirred yogurts, the yogurt is fermented in bulk prior to filling the individual food package container. Thus, the stirred style yogurt typically has a higher viscosity than set style yogurts upon filling due to the lower temperature and the thickening affect of yogurt culture. Nonetheless, the stirred style yogurt typically builds or increases substantially in viscosity after filling over time until reaching its intended finish viscosity. Of course, stirred yogurts also come in various styles and product variations.
Most commonly, fruit preserves or purees are stirred into the stirred yogurt. Such stirred style yogurts comprising intermixed fruit purees are sometimes referred to most frequently as "Swiss" style or, less frequently but equivalently as "Continental" or "French" style. Occasionally, stirred Swiss style yogurts are formulated with excessive amounts of stabilizers with the result that after upon refrigerated storage for 48 hours, the yogurt possesses a solid-like consistency, somewhat reminiscent of custard style yogurt. Such texturally similar products generally result when one manufacturer (whose plants are designed to produce one type of yogurt) desires to produce a product competing with another manufacturer (whose plant is designed to produce the other yogurt type).
More recently, a variation of Swiss style has been marketed that additionally comprises an admixture of nuts and/or partially puffed cereal grains uniformly dispersed through the yogurt. This yogurt mixture is sometimes referred to as "breakfast" style yogurt. The partially puffed grains and nut pieces give a pleasingly mixed organoleptic texture which is both chewy and crunchy in addition to the creamy mouthfeel of stirred yogurt.
Notwithstanding the descriptions of styles given above, such characterizations are only generalizations. Thus, occasionally the prior art will contain a description of, e.g., "western" style yogurt which description may not be exactly as described above. However, the various style names used herein will refer to variants as described above.
As can be appreciated from the above description of the numerous styles and flavors within styles of yogurts, product proliferation and differentiation is an important characteristic of commercial yogurt manufacture. In this highly competitive food product category, there is a continuing desire to develop novel products having distinctive visual, taste, and textural variations in order to stimulate interest in yogurt sales. In particular, it is believed that many consumers will find visually attractive yogurts having distinct regions or layers of different colors but having the texture attributes of a stirred style yogurt. That is, there is an interest in providing a yogurt product comprising a discrete region or portion of one color of a stirred style yogurt and a second region or portion of a different color also comprising a stirred style yogurt. Otherwise stated, there is a need for a stirred style yogurt in a form reminiscent of or competitive with sundae style which is in the form of visually distinct layers.
Three primary difficulties are presented by the development of such a multi-colored product characterized by having discrete layers of color and/or flavor but wherein each phase comprises a stirred style yogurt which problems are particular to stirred style manufacturing.
First, when employing stirred style yogurts, it is very difficult to fill a stirred or fluid yogurt into a cup and advance that cup to a second station wherein the second differently colored yogurt is added to the container. This problem is particularly severe in commercial yogurt product preparation requiring high filling line speeds (e.g., over 40 per minute) such as characteristic of mass production. That is, since the bottom layer is stirred or liquid, the addition of a second, disparately colored overlaying layer of a liquid, cause the two liquid portions immediately to intermix resulting in color blending. Of course, this problem is aggravated when the number of layers is increased so as to have three, four or even more layers.
Second, since the layers are not set as in a custard style yogurt, normal handling can cause the individual stirred style yogurt portions or layers to intermix.
As the skilled artisan will appreciate, the problems associated with providing a multi-layered stirred style yogurt are different from and more challenging than providing a multiple layered custard style product. This is particularly true when the custard style product comprises only two layers and when the layers are compositionally different, e.g., a sundae style yogurt comprises a yogurt layer and a fruit preserve layer.
Still a third problem is that even if it is possible to prepare such a multi-layered stirred style product having each layer of a different color, upon extended storage the color from one layer will tend to migrate or bleed into adjacent layers, leading to a uniformly colored product or large areas of shading of colors.
Given the state of the art in the provision of dairy products, there is a continuing need for new and useful ways to provide stirred style yogurts that are visually attractive.
Another object of the present invention is to provide stirred style yogurts in the form of layers having discrete color to form a multi-layered yogurt product.
Still another object of the present invention is to prepare a multi-layered yogurt product wherein the layers or regions exhibit reduced interphase color and flavor migration.
Still another object of the present invention is to provide multi-phase colored yogurts exhibiting increased resistance to interphase mixing upon normal handling.
Still another object is to provide improved stirred style yogurt products in the form of multiple layers of discretely colored yogurt which layers exhibit minimal interlayer in color bleeding and migration.
Still another object is to provide improved methods for preparing stirred yogurt products in the form of multiple, discretely colored layers exhibiting flatter boundries between layers.
Surprisingly, the above limitations and difficulties have now been overcome and the present invention satisfies the above objectives and a long felt need to develop yogurt products in the form of multiple layers or regions of different color which exhibit minimal color migration or bleeding between layers or regions and minimal yogurt gel destabilization problems. The present yogurt products are fortified with selected stabilizers to provide filling and final viscosities within specified ranges and ratios of viscosities between the layers.